The Making
of Oil

Automobiles and industrial factories
run on oil and coal.How
are oil and coal made?Discovering
the answer to this question will help to explain how we know about
the recycling of carbon within ecosystems.

Oil
and coal are hydrocarbons (made up of hydrogen, about 15% , and carbon, about 85%).To read about a specific example of a hydrocarbon,
click
here.The high-energy fat stored in the body is also made up of
hydrocarbons.The
excess carbon compounds come directly or indirectly from eating the
carbon compounds that plants create during the process of
photosynthesis.

How
do we know that the carbon in oil and gas came from dead plants and
animals? Couldn't the carbon come from volcanoes or hot springs? The
main evidence is that volcanoes only produce simple arrangements of
hydrogen and carbon. The hydrocarbons in oil are very complex and
varied. To make large amounts of oil and gas requires high pressures
and temperatures -- and lots of time (tens of millions of years). The
pressure and temperature can be created when plants and animals become
buried under deep layers of soil and rock. That is why people have
to drill so deep into the earth to find oil.

Much
of our oil and gas probably came from small animals and plants
(plankton) in the ocean (remember that long ago much of the world was
buried under water). Also, some of the carbon in oil could have washed into oceans from rivers.

We
have discovered fossil remains of plants that existed
around 300 million years ago during a time labeled the Carboniferous
period.We can determine
how long ago the plants existed by examining the carbon material of the
plant fossils in a procedure known as
radioactive dating.Essentially,
fossils are mineralized organic materials. When oilmen look for oil,
they look for earth layers that were formed during the Carboniferous
period. When a well is drilled, samples of rock from different
depths are examined under the microscope to see if fossils
from small invertebrates and plants from that time period are present. If
so, odds are that they might hit oil soon.

Fossils from the
Carboniferous period indicate that dinosaurs flourished by eating land plants that grew
in abundance because of the very warm and wet climate.The earth was most likely a huge jungle. Plants and dinosaurs
even grew at the North Pole! And we think there is global warming
today!This
means that our automobiles get their carbon and their energy from the same source as
dinosaurs did 300 million years ago.

Different drainage areas of the United States that
create the Mississippi River. The "hypoxic zone"
seen at the point where the river empties into the Gulf of Mexico
contains so much dirt and plant matter that there is very little
oxygen in the water.

Oil is found deep
in the ground, sometimes several miles deep. How do these
layers of plant and animal matter get buried so deep? As mountains push
up from beneath the earth, rain erodes them, washing away soil and even
cutting massive canyons. The sediment contains soil, sand, and plant and
animal carbon, carrying it all away in rivers that dump into the
ocean. As the sediment settles, it builds up layer upon layer of
carbon-rich material on the ocean floor. The oil that forms eventually
floats up into porous sand formations (which used to be beaches and
river sand bars that have long since become buried).

The big problem
with fossil fuels is that burning them pollutes our air and water with
toxic compounds formed from the burning.
All big cities have so much air pollution that on many days the
air actually looks dirty. Another problem is that the earth's supply of fossil fuels
may be
used up in a few decades. We can get energy in other ways that are not
harmful to the environment (such as windmills,
systems for trapping sun
energy, and
fuel cells. However, these sources usually cost
more than fossil fuels.